Hello everyone,
I had been using the script on my server for dueling "The Argent Crusader"
I scripted him aswell but this is just for Dueling him. Feel Free to create your own Argent crusader but here is the lua:

Code:
function ArgentCrusader_OnSpawn(pUnit, Event)
 ArgentCrusader = pUnit
end

function ArgentCrusader_On_Gossip(pUnit, event, player)
local player = pUnit:GetClosestPlayer()
 pUnit:GossipCreateMenu(117, player, 0)
 pUnit:GossipMenuAddItem(9, "I wish to fight against you!", 318, 0)
 pUnit:GossipMenuAddItem(0, "I was looking for something else...", 434, 0)
 pUnit:GossipSendMenu(player)
end

function ArgentCrusader_Gossip_Submenus(pUnit, event, player, id, intid, code)
 if(intid == 318) then
 pUnit:SetNPCFlags(2)
 pUnit:RegisterEvent("Argent_crusader_Start", 1, 1)
 local name = player:GetName()
 pUnit:SendChatMessage(12, 0, "Prepare to lose "..name..". You will never win!")
 player:GossipComplete()
end

if(intid == 434) then
 player:GossipComplete()
end

end


function Argent_crusader_Start(pUnit, Event)
 pUnit:RegisterEvent("ArgentCrusader_Countdown1", 1000, 1)
 pUnit:RegisterEvent("ArgentCrusader_Countdown2", 2000, 1)
 pUnit:RegisterEvent("ArgentCrusader_Countdown3", 3000, 1)
 pUnit:RegisterEvent("ArgentCrusader_Flags", 4000, 1)
end

function ArgentCrusader_Countdown1(pUnit, Event, player)
 local player = pUnit:GetClosestPlayer()
 player:SendBroadcastMessage("Duel starts in 3...")
end

function ArgentCrusader_Countdown2(pUnit, Event, player)
 local player = pUnit:GetClosestPlayer()
 player:SendBroadcastMessage("Duel starts in 2...")
end

function ArgentCrusader_Countdown3(pUnit, Event, player)
 local player = pUnit:GetClosestPlayer()
 player:SendBroadcastMessage("Duel starts in 1...")
end

function ArgentCrusader_Flags(pUnit, Event)
 pUnit:SetNPCFlags(2)
 pUnit:SetFaction(14)
end


function ArgentCrusader_OnCombat(pUnit, Event)
 pUnit:RemoveEvents()
 pUnit:RegisterEvent("ArgentCrusader_Spell1", 1000, 1)
 pUnit:RegisterEvent("ArgentCrusader_Spell2", 15600, 0)
 pUnit:RegisterEvent("ArgentCrusader_End", 100, 0)
 pUnit:RegisterEvent("ArgentCrusader_Check", 100, 0)
end

function ArgentCrusader_Spell1(pUnit, Event)
 pUnit:CastSpell(41924)
end

function ArgentCrusader_Spell2(pUnit, Event)
 pUnit:FullCastSpellOnTarget(853, pUnit:GetClosestPlayer())
end


function ArgentCrusader_OnLeave(pUnit, Event)
 pUnit:RemoveEvents()
 pUnit:SetCombatCapable(0)
 pUnit:SetFaction(35)
 pUnit:SetNPCFlags(1)
 pUnit:SetHealthPct(100)
 pUnit:RemoveAllAuras()
 pUnit:ReturnToSpawnPoint()
end


--[[ If Player has under 20% life ]]--


function ArgentCrusader_Check(pUnit, Event)
local player = pUnit:GetClosestPlayer()
if player:GetHealthPct() < 20 then
 pUnit:RemoveEvents()
 pUnit:SetFaction(35)
 pUnit:SetCombatCapable(1)
 pUnit:SetNPCFlags(1)
 pUnit:RegisterEvent("ArgentCrusader_OnWin", 500, 1)
end
end

function ArgentCrusader_OnWin(pUnit, Event)
 pUnit:CastSpell(8203)
 pUnit:RegisterEvent("ArgentCrusader_InvisibleRemoveWin", 500, 1)
end

function ArgentCrusader_InvisibleRemoveWin(pUnit, Event)
 pUnit:RemoveAura(8203)
 pUnit:RegisterEvent("ArgentCrusader_TalkWin", 500, 1)
end

function ArgentCrusader_TalkWin(pUnit, Event, player)
 pUnit:SendChatMessage(12, 0, "You puny weakling, you shall never match the might of the argent crusader!")
 pUnit:Emote(1, 2000)
 pUnit:RegisterEvent("ArgentCrusader_Return", 1500, 1)
end


--[[ If Argent crusader has under 20% life ]]--


function ArgentCrusader_End(pUnit, Event)
local player = pUnit:GetClosestPlayer()
if pUnit:GetHealthPct() < 20 then
 if player:HasQuest(897579) == true then
  player:MarkQuestObjectiveAsComplete(897579, 0)
  pUnit:RemoveEvents()
  pUnit:SetFaction(35)
  pUnit:SetNPCFlags(2)
  pUnit:SetCombatCapable(1)
  pUnit:RegisterEvent("ArgentCrusader_Invisible", 100, 1)
  else
   if player:HasQuest(897575) == true then
   player:AddItem(87542, 1)
   pUnit:RemoveEvents()
   pUnit:SetFaction(35)
   pUnit:SetNPCFlags(2)
   pUnit:SetCombatCapable(1)
   pUnit:RegisterEvent("ArgentCrusader_Invisible", 100, 1)
   else
    pUnit:RemoveEvents()
    pUnit:SetFaction(35)
    pUnit:SetNPCFlags(2)
    pUnit:SetCombatCapable(1)
    pUnit:RegisterEvent("ArgentCrusader_Invisible", 100, 1)
  end
  end
end
end

function ArgentCrusader_Invisible(pUnit, Event)
 pUnit:CastSpell(8203)
 pUnit:RegisterEvent("ArgentCrusader_InvisibleRemove", 500, 1)
end

function ArgentCrusader_InvisibleRemove(pUnit, Event)
 pUnit:RemoveAura(8203)
 pUnit:RegisterEvent("ArgentCrusader_Talk", 500, 1)
end

function ArgentCrusader_Talk(pUnit, Event, player)
 pUnit:SendChatMessage(12, 0, "I lost! The Argent Champion! This is immpossible.")
 pUnit:Emote(398, 3000)
 pUnit:RegisterEvent("ArgentCrusader_Return", 4000, 1)
end

function ArgentCrusader_Return(pUnit, Event)
 pUnit:SetCombatCapable(0)
 pUnit:SetNPCFlags(1)
 pUnit:WipeTargetList()
 pUnit:RemoveAllAuras()
 pUnit:ReturnToSpawnPoint()
 pUnit:Despawn(3000, 5000)
end


RegisterUnitEvent(780215, 1, "ArgentCrusader_OnCombat")
RegisterUnitEvent(780215, 2, "ArgentCrusader_OnLeave")
RegisterUnitEvent(780215, 18, "ArgentCrusader_OnSpawn")
RegisterUnitGossipEvent(780215, 1, "ArgentCrusader_On_Gossip")
RegisterUnitGossipEvent(780215, 2, "ArgentCrusader_Gossip_Submenus")
Code:
INSERT INTO `creature_names` VALUES ('780215', 'Argent Crusader', 'The Crusader', '', '0', '7', '0', '0', '0', null, '28587', '0', '0', '0', '1', '1', '1', '0', '0', '0', '0', '0', '0', '0');

INSERT INTO `creature_proto` VALUES ('780215', '80', '80', '35', '200000', '300000', '547862', '1', '3', '2200', '0', '2300', '3100', '0', '0', '0', '0', '36000', '100', '70', '70', '70', '70', '70', '70', '1', '0', '0', '0', '0', '0', '0', '2.5', '8', '14', '0', '0', '0', '0', '0', '0', '0', '0', '0', '0');
Pics: